A biarylphosphine compound is frequently used as a ligand of a transition metal complex. The complex is extensively used as a good catalyst for various organic reactions. As the organic reaction in which the transition metal complex is effective as a catalyst, there may be mentioned a cross-coupling reaction in which a halogenated aryl is reacted with an arylboronic acid or a primary/secondary amine to obtain a corresponding biaryl compound or arylamine compound, and a hydroformylation reaction in which an aldehyde is synthesized by the carbon homologation of alkenes with carbon monoxide.
A biarylphosphine compound is a useful compound in an extensive field including the ligand as mentioned above. However, in the existing synthetic methods, an expensive material is often used as a starting raw material and the synthesis is often accompanied by danger.
The process for producing a biarylphosphine compound, which has been reported up to now, may be classified into the following two techniques.
As the first production process, for example, as shown in the following reaction formula, there may be mentioned a technique in which a halogenated biaryl is metalized with magnesium or lithium, followed by coupling a halogenophosphine (U.S. Pat. No. 6,307,087 and U.S. Pat. No. 7,026,498).

Although the production process is a useful technique because an intended product may be obtained in a reasonable yield the halogenated biaryl as a starting raw material is frequently difficult to obtain commercially. In addition, an absolute anhydrous condition is required for handling an organic metal and the handling is accompanied by danger because an organic metal itself is pyrophoric. Further, the production method has a limitation on the scope of the application, for example, it is not applicable to a substrate having a functional group reacting with an active organic metal, and the like.
As the second production process, there may be mentioned a technique in which a halogenated biaryl or biarylsulfonate is cross-coupled to a hydrogen-phosphine compound in the presence of a catalyst and a base. The production process may be shown, for example, by the following reaction formula (U.S. Pat. No. 6,124,476).

X in the reaction formula generally includes a halogen or a sulfonate (the example in U.S. Pat. No. 6,124,476 is a bromo group). If X is a sulfonate, since Biaryl-X may be easily obtained from an inexpensive phenol compound and a sulfonic acid anhydride or a halide, it is industrially advantageous in many cases. However, in practice, if there is used an inorganic base such as NaOt-Bu or KOt-Bu which is generally frequently used as a base as shown by the reaction formula, the sulfonate is hydrolyzed, thus significantly reducing the yield of the intended product in many cases.
As an improved process when a sulfonate is used as a raw material in the production process using the inorganic base, there is disclosed a production process in which an organic base is used in place of the inorganic base in order to prevent hydrolysis, for example, as shown by the following reaction formula (U.S. Pat. No. 5,399,771 and U.S. Pat. No. 6,333,435).

As the organic base used in the production process, there may be mentioned triethylamine, triisopropylamine, tributylamine, triethylenediamine (DABCO) and the like, and preferably used is DABCO. The production process is effective if a diarylphosphine is used as a hydrogen-phosphine compound as a starting raw material. However, the production process is not industrially applicable because the yield is low if a monoaryl monoalkyl phosphine or a dialkylphosphine is used as a hydrogen-phosphine compound.
In addition, in the second process, there is proposed a technique in which when a halogenated biaryl or biarylsulfonate is cross-coupled to a halogenophosphine by using the halogenophosphine in place of a hydrogen-phosphine compound, a reducing substance is used in addition to a catalyst and a base.

In the production process, as the reducing substance, there may be used zinc powders (Chemical Communications 2359 (1997)), hydrogen (JP2000-7688A), sodium borohydride/lithium aluminum hydride (U.S. Pat. No. 7,208,633) and the like. The production process is effective if a halogenodiarylphosphine is used as a halogenophosphine, which is a starting raw material. However, as with the improved process using the organic base, the production process is not industrially applicable because of the yield is low if a monoaryl monoalkyl halogenophosphine or dialkylhalogenophosphine is used as a halogenophosphine.
Accordingly, in the present technical field, there has been desired a production process of obtaining biarylphosphine compounds by coupling a biarylsulfonate compound to an organic phosphine compound in an industrially advantageous manner.